Channel Correlation Based Zero-Forcing Beamforming in Two-User MISO Broadcast Channel

In this paper, a novel zero-forcing beamforming (ZFBF) is presented for the two-user multiple input single output broadcast channel. Based on the knowledge of channel correlations at the transmitter side, a nonlinear optimization problem is formulated to determine the beamformers so that the weighted ergodic sum-rate is maximized subject to avoiding multi-user interference and meeting a total power constraint. By factorizing each beamformer, the original complicated problem can be transformed into a simpler one. Numerical results show that the performance gap between the proposed ZFBF and the traditional instantaneous channel state information based ZFBF is within 1.5 bits per transmission.